When sewing garments, or other articles, with semi-automatic sewing machines, when the sewing of one garment has been completed and an operator lets up on the foot pedal for controlling the sewing machine, it takes a significant period of time before the automatic sewing machine stops stitching the thread chain. During the time that the needle of the sewing machine is still moving, but stitching of the garment has been completed, a thread chain about 1-11/2 inches in length may be formed. While conventionally the thread chain can be severed so that not too long a portion thereof extends from the rear of the garment, when sewing is restarted on a second garment the thread chain often extends from the front of the second garment and spoils the appearance of the garment. Therefore, in the conventional commercial practice, the thread chain must be cut off manually, resulting in labor costs that are higher than desirable, and disrupting the ability to automate the garment handling operations.
It has been recognized in the art that it is desirable to fold back the chain stitching so that it will be stitched onto the trailing garment, as exemplified by U.S. Pat. No. 4,038,933. However heretofore there have been a number of practical difficulties associated with producing commercial machines to successfully perform that function, and at the present time there are no known commercial machines in widespread use which do perform the folding-back and stitching function.
According to the present invention an attachment for an automatic sewing machine, and a method of automatically stitching excess thread chain, are provided which result in practical and effective stitching of excess thread chain to a subsequent garment. The attachment and the method according to the present invention are completely automatic so that no operator intervention is necessary; in fact the operator need not even let up on the foot pedal for controlling the semi-automatic sewing machine once the stitching has been completed.
According to one aspect of the present invention, an attachment is provided for a semi-automatic sewing machine having a stitching needle for stitching a thread chain, a presser foot, and a power source. The attachment comprises the following components: A means for sensing the completion of stitching, by the sewing machine, of a first garment, by sensing a trailing portion of the first garment. A means for automatically engaging the first garment in response to the sensing and moving the first garment from the stitching needle more quickly than the sewing machine stitches the thread chain, to pull excess thread chain extending past the trailing portion of the first garment relatively taut. A means for automatically severing the excess thread chain from the trailing portion of the first garment when the excess thread chain is relatively taut; and a means for automatically positioning the excess thread chain with respect to a second garment so that the excess thread chain is stitched to the second garment by the sewing machine.
The automatic sensing preferably is provided by utilizing an electric eye including a target mounted on the base plate of the sewing machine, and the light emitting and sensing mechanism mounted above the target.
The means for automatically engaging the first garment preferably comprises a wheel having the garment engaging portions thereof of rubber, or another elastic material. The wheel is rotated about an axis perpendicular to the direction of the garment movement, and cooperates with the flat surface of the sewing machine to propel the garment away from the needle when an arcuate circumferential portion of the wheel (about 270.degree. of its circumference) is above the surface. Once cut-out (scalloped) portions of the wheel periphery are above the surface, however, the wheel no longer engages the garment even though it continues rotation. At that point the excess thread chain is taut.
The automatic severing means preferably comprises a stationary plate having an edge, the plate disposed between the stitching needle and the wheel. A rotatable plate having an edge cooperating with the edge of the stationary plate is rotated by a shaft to effect severing. A linear actuator is connected to the shaft to effect the rotation.
The means for automatically positioning the excess thread chain comprises a pair of air jets which are blowing means for blowing the threaded chain from its severing position to a position on the opposite side of the stitching needle. A catcher, comprising a catching finger actuated by a linear actuator, and cooperating with a block of rubber, grabs the excess thread chain and holds it in place, while gradually releasing it as it is being stitched into the next garment by the sewing machine.
Means are provided for automatically stopping the stitching action of the sewing machine and raising the presser foot in response to sensing of the trailing portion of the first garment. This means comprises a linear actuator operatively connected between an arm for engaging and disengaging the clutch of the sewing machine, and the foot pedal for operating the sewing machine, and a rod having an enlarged actuator thereon. The linear actuator includes a movable portion thereof which has an abutment for engaging the enlarged portion of the rod, and means for effecting actuation of the linear actuator to move the abutment--in response to the sensing--away from the enlarged attachment to the rod so that the rod does not engage the abutment, thereby causing the arm to move to a clutch disengaging position. A resetting switch is provided on the abutment which is engaged by the rod enlarged portion to reset the components so that the operator, by manipulation of the foot pedal can start the next stitching cycle.
The invention also comprises the individual components of the attachment as described above, which may cooperate with other types of components for performing the same function as the preferred components according to the invention, to produce the desired result.
The invention also relates to a method of automatically stitching excess thread chain to a cloth so that no free stitches are provided on the leading edge of the cloth. The method comprises the steps of: (a) Automatically sensing the completion of stitching, by the sewing machine, of a first cloth, by sensing a trailing portion of the first cloth. (b) Automatically engaging the first cloth in response to the sensing and moving the first cloth away from the stitching needle more quickly than the sewing machine stitches the thread chain, to pull excess thread chain extending past the trailing portion of the first cloth relatively taut. (c) Automatically severing the excess thread chain from the trailing portion of the first garment when the excess thread chain is relatively taut. And (d) automatically positioning the excess thread chain with respect to a second cloth so that the excess thread chain is stitched to the second cloth by the sewing machine, so neither cloth has free stitches extending therefrom.
It is the primary object of the present invention to provide a simple, effective, and practical method and attachment (including components thereof) for automatically stitching excess thread chain to a trailing cloth in the operation of a semiautomatic sewing machine. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.